• Journal of Welding and Joining
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• v.20 no.2
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• pp.50-58
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• 2002

Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)

• Journal of Industrial Technology
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• v.16
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• pp.131-137
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• 1996

For a large scale civil and architectural structures, mainly steel, concrete and aluminum have been used and weight and corrosion of materials became a major concern. Designing with composite materials is very much complicated. Simple classical theory may yield good results for selecting "initial" sections for preliminary design. D. H. Kim proposed to use the quasi-isotropic constants by Tsai for the preliminary design of the composite primary structures for the civil construction. Also he made simple equation using correction factor. In this paper, the simple formulas developed by D. H. Kim to obtain "exact" values of the natural frequencies of [ABBCAAB]r laminate are compared with Whitney's equations. Also natural frequencies of the plate with varying aspect ratios and reinforcing fiber orientations, are compared with natural frequencies of bean. This work can be a guideline to obtain data in many other cases.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.76-84
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• 1999

The residual stress generated when the steel plates were produced, did not influence on the out-of-plane deformation and residual stress generated by welding. When the initial deflection shape was a concave(Type I), the out-of-plane deformation became the same shape as that of the initial deflection and its magnitude became small. When the initial deflection made a winding in the welding direction(Type III), the out-of-plane deformation became large in the plate width. The initial deflection shape did not influence on residual stress and plastic strain produced by welding.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.1-10
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• 2008

Residual stress caused in the weldments with high restraint force are often during welding observed in the weldments of large size nozzles or radial tanks. The reason is that quantitative analysis about thermal stresses during welding is lack for this weldments. To verify Finite Elements Method(FEM) theory, the temperature was measured with thermocouple in a real time in this paper. Also analysis of the thermal stress for welding condition is performed by ABAQUS program package on various welding condition in 304 stainless steel butt welding.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.181-184
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• 2006

In this investigation, fracture mechanism of the pre-cracked beams strengthened with FRP-Rod and GSP(Glass Fiber-Steel Plate) were experimentally studied by the repeating load test according to the three different loading speeds. In the experiments, it was identified that pre-crack in the damaged beams led the significant fracture type of the strengthened beams and loading speed did not influence the behaviors of the fractures. On the other hand, strengthened beams by GSP have more large increasing effects of the strength comparing to beams strengthened with FRP-Rod, but they have a brittle behaviors in fracture.

• KIEAE Journal
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• v.7 no.5
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• pp.143-148
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• 2007

The application of metal deck floor system is increasing gradually and especially for office buildings. In the cases of large parking structures and storage structures, the construction period and the cost can be reduced. Also the steel deck system can prevent the crack of a floor and reduce the retrofit expenses. However, the floor should stand for the repeated truck load which is relatively heavier repeated loading. The mechanical behavior of a slab under repeated load is also different from the static loading state. An evaluation of a structural capacity was performed in this study through the dynamic capacity evaluation experiment for an application of a composite deck floor system as a parking structure slab. The period of repeated loadings were set up as 25years and 960,000 times monotone cyclic loads were applied at the center of the specimens. The tension crack propagation and patterns at the center of specimens were examined.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.1
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• pp.69-76
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• 2020

Bridges which are components of road network consume large amounts of resources such as concrete and steel materials, which have large environmental impacts during construction. This causes a great environmental burden. In order to reduce the environmental impact caused by the construction of the bridge, the environmental impact should be reviewed based on reasonable data in the early design stage. The purpose of this study is to provide basic data for LCA-based environmental impact assessment in the process of selecting bridge type in the early design stage. For this purpose, design data for four types of PSC bridges (general PSC girder, IPC girder, e-Beam, DR girder) were collected and LCA was performed to analyze the basic unit value and impact factors of environmental load. The results of the analysis showed that the environmental impact of IPC girder was the smallest, and the environmental impact of e-Beam was 133.7% higher than that of IPC girder. In addition, concrete, reinforcement, PC strand, square timber, sheath pipe, and steel plate were derived as the main factors that generate 98.5% of the overall environmental impact of PSC girder.

• International Journal of Korean Welding Society
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• v.3 no.2
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• pp.40-45
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• 2003

A series of experiments has been carried out to investigate the effect of titanium, boron and nitrogen on the microstructure and toughness of simulated heat affected zone (HAZ) in quenched and tempered (QT) type 490MPa yield strength steels. For acquiring the same strength level, the carbon content and carbon equivalent could be lowered remarkably with a small titanium and boron addition due to the hardenability effect of boron during quenching process. Following the thermal cycle of large heat input, the coarsened grain HAZ (CGHAZ) of conventional quenched and tempered (QT) type 490MPa yield strength steels exhibited a coarse bainitic or ferrite side plate structure with large prior austenite grains. While, titanium and boron bearing QT type 490MPa yield strength steels were characterized by the microstructure in the CGHAZ, consisting mainly of the fine intragranular ferrite microstructure. Toughness of the simulated HAZ was mainly controlled by the proper Ceq level, and the ratio of Ti/N rather than titanium and nitrogen contents themselves. In the titanium­boron added QT steels, the optimum Ti/N ratio for excellent HAZ toughness was around 2.0, which was much lower than the known Ti/N stoichiometric ratio, 3.4. With reducing Ti/N ratio from the stoichiometric ratio, austenite grain size in the coarse grained HAZ became finer, indicating that the effective fine precipitates could be sufficiently obtained even with lower Ti/N level by adding boron simultaneously. Along with typical titanium carbo­nitrides, various forms of complex titanium­ and boron­based precipitates, like TiN­MnS­BN, were often observed in the simulated CGHAZ, which may act as stable nuclei for ferrite during cooling of weld thermal cycles

• Structural Engineering and Mechanics
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• v.14 no.4
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• pp.455-472
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• 2002

The paper involves the study on the elastic and elasto-plastic stress wave propagation in the 1-D and 2-D solid media. The Smooth Particle Hydrodynamics equations governing the elastic and elasto-plastic large deformation dynamic response of solid structures are presented. The proposed additional stress points are introduced in the formulation to mitigate the tensile instability inherent in the SPH approach. Both incremental rate approach and leap-frog algorithm for time integration are introduced and the new solution algorithm is developed and implemented. Two examples on stress wave propagation in aluminium bar and 2-D elasto-plastic steel plate are included. Results from the proposed SPH approach are compared with available analytical values and finite element solutions. The comparison illustrates that the stress wave propagation problems can be effectively solved by the proposed SPH method. The study shows that the SPH simulation is a reliable and robust tool and can be used with confidence to treat transient dynamics such as linear and non-linear transient stress wave propagation problems.

• Steel and Composite Structures
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• v.14 no.4
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• pp.335-347
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• 2013

In this paper, the nonlinear cylindrical bending behavior of functionally graded nanocomposite plates reinforced by single-walled carbon nanotubes (SWCNTs) is studied using an efficient and simple refined theory. This theory is based on assumption that the in-plane and transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTCRs) are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The fundamental equations for functionally graded nanocomposite plates are obtained using the Von-Karman theory for large deflections and the solution is obtained by minimization of the total potential energy. The numerical illustrations concern the nonlinear bending response of FG-CNTRC plates under different sets of thermal environmental conditions, from which results for uniformly distributed CNTRC plates are obtained as comparators.